Electronic components are everywhere, from smartphones to cars to home appliances, and form the basis of modern technology. Understanding how electronic components work is critical to designing and maintaining these devices. As a result, INFINITECH has put together a comprehensive guide on how electronic components work, which you can benefit from whether you are a beginner or an engineer with some experience.

Functions and principles of basic electronic components

How does a resistor limit current?

Resistors limit current through their own resistance characteristics. According to Ohm's law, voltage (V) is equal to current (I) multiplied by resistance (R), i.e. V = I × R.

When a resistor is plugged into a circuit, it blocks the flow of electrons, which reduces the current. If there is a certain voltage in the circuit, then the current through the resistor will be determined by the resistance value of that resistor. For example, if a resistor has a resistance of 100 ohms and the voltage at its ends is 10 volts, then the current passing through it will be 10 volts divided by 100 ohms, which is 0.1 amps (or 100 mA). In short, the resistor reduces the current by providing a physical barrier, the size of which depends on the resistance value of the resistor.

How do capacitors store charge?

How does the inductor control the current change?

An inductor is an electronic component capable of storing energy from a magnetic field, which affects the current in a circuit primarily by preventing rapid changes in the current. An inductor is usually made of wire wound into a coil, and when current flows through the coil, it creates a magnetic field around it. The operating principle of the inductor is based on Faraday's law of electromagnetic induction, which states that changes in the magnetic flux passing through a closed loop create an electromotive force (EMF). Specifically, when the current in the inductor changes, due to the change in the magnetic field, a reverse electromotive force (called self-induced electromotive force) is generated that is proportional to the rate of change of the current. This reverse electromotive force tries to stop the current from changing.

When the current begins to increase, the magnetic field around the inductor also increases. According to Lenz's law, an inductor creates a reverse electromotive force in an attempt to prevent an increase in current. As a result, the inductor delays the rate at which the current rises. When the current starts to decrease, so does the magnetic field. The inductor again generates a reverse electromotive force, this time to maintain the current constant. This electromotive force tries to keep the current constant, thus slowing down the rate at which the current falls. In the process of changing the current, the energy of the magnetic field is stored in the inductor. When the current is stabilized, the inductor no longer produces a significant reverse electromotive force, and the energy is stored in the form of a magnetic field.

Whether the current is increased or decreased, the inductor will produce a reverse electromotive force to resist this change, thus playing a role in controlling the current change. This feature makes inductors a key element in many circuit designs, especially in AC signal processing, filtering circuits, energy storage, and power conversion.

The working mechanism of semiconductor components

How do transistors work?

A transistor is an important semiconductor device that can be used to amplify electrical signals or act as a switch. Common transistor types include bipolar transistors (BJTS) and metal-oxide-semiconductor field-effect transistors (MOSFETs).

There are two types of bipolar transistors (BJT) : NPN and PNP. A type NPN transistor consists of three layers of semiconductor material: two N-types (emitter E and collector C) sandwiched by a P-type (base B). Pnp-type transistors are two P-types (emitter E and collector C) sandwiched by an N-type (base B). It works by the fact that when a small forward bias voltage is applied to the base relative to the emitter, some carriers (electrons or holes) are injected from the emitter into the base region. Most of the injected carriers will pass through the base (because the base is thin) to the collector, creating a collector current. The collector current increases significantly due to the presence of base current, which allows the BJT to amplify the current. In terms of amplification, the collector current of the BJT is proportional to the base current, and the proportional coefficient is called the current gain (β or hFE). By controlling the size of the base current, the collector current can be adjusted to realize the signal amplification.

Figure: Bipolar transistor (BJT) structure and working principle

Metal-oxide-semiconductor field-effect transistor (MOSFET) is a voltage controlled transistor, which is mainly divided into two types: enhancement type and depletion type. It consists of a source (S), a gate (G), a drain (D) and a substrate (B). The gate is isolated from the channel area by a layer of insulation (usually silica). When a voltage (VGS) is applied between the gate and the source, an electric field is created beneath the insulation. For n-channel MOSFETs, forward-biased VGS attract electrons in the P-type substrate below the gate, forming a conductive N-type channel. The conductivity of the channel depends on the size of the VGS, which in turn affects the current (IDS) from the source to the drain. When the VGS is large enough, the channel becomes on-enabled, allowing a larger current to flow from the source to the drain, and the MOSFET is in the "on" state. When the VGS is less than the threshold voltage, the channel is closed, almost no current flows, and the MOSFET is in the "off" state.

Whether it is a BJT or a MOSFET, they can control a large current at the output by controlling a small current or voltage at the input, thus enabling signal amplification or switching functions. BJT uses current control, while MOSFET uses voltage control. Both types of transistors have a wide range of applications in electronic circuits, such as amplifier circuits, switching circuits, oscillators, etc.

How do diodes work?

A diode is a semiconductor device that has unidirectional conductivity, meaning that the current can only pass in one direction. There are many kinds of diodes, including ordinary diodes, light-emitting diodes (leds), photodiodes, etc. Below, INFINITECH describes the working principles of several common diodes.

A common diode consists of a PN junction composed of a P-type semiconductor and an N-type semiconductor. A space charge region is formed at the PN junction, called the depletion layer. When a forward voltage is applied (P terminal is connected to the positive terminal of the power supply, N terminal is connected to the negative terminal of the power supply), the depletion layer Narrows and allows current to pass through. When a reverse voltage is applied, the depletion layer widens, preventing current from passing through.

Light-emitting diode (LED) is also a PN-junction diode, but its material is specially treated so that it can emit light when the pilot passes through. When the LED is forward-biased, electrons pass through the depletion layer from the N region into the P region, recombining with the hole. When electrons and holes recombine, energy is released and light is emitted in the form of photons. Different semiconductor materials correspond to different band gaps, so they can emit different colors of light.

A photodiode is a special type of diode that usually operates in a reverse-biased state. Its PN junction is larger in order to receive more light. When light hits the PN junction of the photodiode, the energy of the photon can make the electron jump from the valence band to the conduction band, forming an electron-hole pair. Under reverse bias, these electron-hole pairs separate within the depletion layer, generating an electric current. Photodiodes can convert optical signals into electrical signals and are commonly used in optoelectric detection and conversion applications.

The working principle of the diode is based on the characteristics of the PN junction. In the case of ordinary diodes, their unidirectional conductivity allows the current to pass in only one direction. For leds, when forward-biased, electrons are combined with holes to produce light. In the case of photodiodes, under reverse bias, the electron-hole pairs generated by light irradiation will be separated, generating an electric current. These properties allow diodes and their variants to play an important role in a variety of electronic and optoelectronic applications.

Why does Zener diode have voltage regulation characteristics?

Zener diode is a kind of special diode, which has unique voltage regulation characteristics when it is reverse-biased. It is similar to an ordinary diode, consisting of a PN structure composed of a P-type semiconductor and an N-type semiconductor. However, the design of the Zener diode allows it to have a lower breakdown voltage, and it is easier to reach a breakdown state when reverse biased.

When the Zener diode is reversely biased, that is, the N-type side is connected to the positive electrode of the power supply, and the P-type side is connected to the negative electrode of the power supply, and the diode is in the cut-off state. With the increase of the reverse voltage, the diode will reverse breakdown when the voltage reaches the Zener voltage (Vz). At this voltage, the electric field in the depletion layer inside the diode is strong enough to make the electrons jump from the valence band to the conduction band, producing a large number of electron-hole pairs. Once the Zener diode enters the breakdown state, even if the reverse current increases, the voltage at both ends (i.e. the Zener voltage Vz) remains almost constant. This means that no matter how the input voltage changes, as long as the current is sufficient, the voltage at both ends of the Zener diode will be stable around Vz. In the breakdown state, the Zener diode consumes excess power, converting it into heat to maintain a stable output voltage. Zener diodes are often used in voltage regulator circuits as a reference voltage source to ensure voltage stability in the circuit. They are also used as overvoltage protection, preventing other components in the circuit from being damaged by too high a voltage.

It can be seen from its principle that the reason why Zener diodes have voltage regulation characteristics is that under their specific reverse breakdown voltage, even if the current changes, the voltage at both ends of the diode can remain relatively stable. This characteristic makes Zener diodes a common voltage stabilizer and protection element in electronic circuits.

Basic concept of integrated circuit

How are components integrated inside an integrated circuit?

An integrated circuit (IC) is a tiny electronic device that integrates a large number of electronic components (such as transistors, resistors, capacitors, etc.) onto a small piece of semiconductor material (usually silicon). Here is an overview of the process of how various components are integrated inside an integrated circuit:

Manufacturing process

High purity silicon is used to make wafers. The wafer surface is chemically cleaned to remove impurities and ensure a clean surface. Impurities (such as boron or phosphorus) are introduced into silicon wafers by diffusion or ion implantation to form P-type or N-type semiconductor regions. These doping regions make up the various components in the integrated circuit, such as the source, gate, drain, and so on. The photoresist is used to form a pattern on the wafer surface, and then the design pattern is transferred to the wafer through the exposure and development steps. This process can be repeated many times to build complex multi-layered structures.

A layer of metal (such as aluminum or copper) is deposited on the wafer surface to make interconnects. Insulating layers or other functional materials can also be deposited. The unwanted parts are removed by chemical or plasma etching techniques to form the desired lines and component shapes. A protective film is deposited on top of the finished integrated circuit to prevent corrosion and mechanical damage. The finished integrated circuit is cut into individual chips. The chip is installed in the package and connected with external pins to facilitate connection with other electronic components.

Component integration

• The transistor is formed by precisely controlling the doping concentration and geometry.

• A resistor is formed using a material with high resistivity or through a silicon region of appropriate length and width.

• A capacitor is formed by placing a layer of insulating material between two layers of conductors.

• Different components are connected by depositing metal layers and patterning on them.

The fabrication of integrated circuits is a complex and sophisticated process that involves multiple steps, including wafer preparation, doping, lithography, film deposition, etching, passivation layers, and packaging. Through these steps, thousands of electronic components can be integrated on a single silicon chip to form highly integrated miniature electronic systems. This high degree of integration not only reduces the size and weight of the circuit, but also improves reliability and reduces costs, and is the basis of modern electronic technology.

What are the differences between different types of integrated circuits?

Analog integrated circuit

Analog integrated circuits deal with continuously changing signals, which can represent various physical quantities such as sound, temperature, and pressure. It is usually used for signal amplification, filtering, frequency conversion and other operations to improve signal quality or adapt to different application needs. It can implement nonlinear processing, such as logarithmic and exponential transformations, multiplication and division operations. Analog signals are susceptible to noise, so careful design is needed to improve the signal-to-noise ratio of the signal. Analog integrated circuits are widely used in audio processing, signal regulation, control system, communication system and so on.

Analog integrated circuits deal with continuously changing signals that can represent a variety of physical quantities, such as sound, temperature, and pressure. They are usually used for signal amplification, filtering, frequency conversion and other operations to improve signal quality or adapt to different application needs. Analog circuits can also implement nonlinear processing, such as logarithmic and exponential transformations, multiplication and division operations. Since analog signals are susceptible to noise, careful design is needed to improve the signal-to-noise ratio of the signal. Analog integrated circuits are widely used in audio processing, signal conditioning, control systems and communication systems.

Digital integrated circuit

Digital integrated circuits deal with signals in discrete, binary form, usually represented as high (1) and low (0) levels. They are mainly used to perform logical operations, such as and gates, or gates, not gates, etc., as well as more complex logical functions, such as adders, counters, registers, etc. Digital signals have a strong ability to resist interference because they only recognize specific level states. Digital integrated circuits are easy to achieve large-scale integration and can integrate a large number of logic gates and storage units together. Digital integrated circuits are widely used in microprocessors and microcontrollers (such as computer cpus, control chips of embedded systems), memory (such as RAM, ROM), interface circuits (such as USB controllers, Ethernet controllers) and data converters (such as analog-to-digital converters (ADC), digital-to-analog converters (DAC)) and other fields.

The difference between the two

The main difference between analog integrated circuits and digital integrated circuits is the way they process signals. Analog integrated circuit processes continuously changing signals and is suitable for signal amplification, filtering and other applications. Digital integrated circuits deal with discrete binary signals, which are mainly used for logic operations and data processing. Although there are obvious differences in design and application, in practical applications, analog and digital circuits often need to work together to complete complex functions. For example, in modern electronics, analog circuits are used to process sensor signals, while digital circuits are responsible for data processing and control tasks.

Logic gates and other digital circuit elements

How do common logic gates implement logical operations?

A logic gate is the basic building block of a digital circuit, used to perform basic logical operations. Common logic gates include AND gates, OR gates, and NOT gates. And how do these logic gates implement logical operations?

AND door (AND)

With a gate there are two or more inputs and one output. When all inputs are high level, the output is high level. Otherwise, the output is low. And gates can be implemented in series with two or more transistors, such as BJTS or MOSFETs. When all input transistors are on, the output will be high.

OR gate (OR)

A OR gate has two or more inputs and one output. The output is high as long as one or more inputs are high; The output is low level only when all inputs are low level. Or gates can be realized by two or more transistors in parallel. As long as any of the input transistors are on, the output will be high.

NOT gate

A non-gate has only one input and one output. The input is high power level, and the output is low. And vice versa. A non-gate can be achieved by a transistor (such as a MOSFET) and a resistor in series. When the input level is high, the transistor is on, and the output becomes low through resistance ground; Conversely, the transistor shuts off and the output becomes high through the power supply.

Other logic gate

In addition to the above three basic logic gates, there are other logic gates, such as XOR gate (XOR), same or gate (XNOR), and not gate (NAND), or not gate (NOR). These gates can be implemented by combining basic and gates, or gates and not gates.

What is the basic working principle of an op amp?

The operational amplifier (Op-Amp) is a highly flexible electronic component that is widely used in a variety of analog signal processing circuits. It usually has two inputs and one output: the in-phase input (+) receives the input signal in phase with the output signal; Inverting input (−) receives an input signal that is inverting the output signal; The output end (Vout) is the port of the output signal.

Special components and their applications

How is the transformer boosted or depressed?

A transformer is an electrical device used to change alternating current voltage, consisting mainly of two coils (primary and secondary) and an iron core (usually made of ferromagnetic material). The two coils are wound around the same iron core, but are insulated from each other and have no direct electrical connection. When alternating current passes through the primary coil, it creates a changing magnetic field. This magnetic field is coupled through the core to the secondary coil, where a voltage is induced. According to Faraday's law of electromagnetic induction, the voltage in the secondary coil is proportional to the voltage in the primary coil to their respective turns ratio.

The transformer transformer ratio refers to the ratio of turns of the primary coil and the secondary coil, expressed by the formula n=N2/N1, where N1 is the number of _turns of the primary coil and N2 is the number of _turns of the secondary coil. If n > 1, the transformer is a booster transformer. If n < 1, the transformer is a step-down transformer. Transformers play a vital role in power systems, used in power plants, transmission and distribution systems, and various electronic devices to ensure proper voltage conversion and stable power supply.

What are the characteristics of special types of resistors?

Special types of resistors, such as variable resistors and thermistors, have their own unique characteristics and uses.

Figure: Thermistor resistance value and temperature change

For example, the resistance value of a variable resistor can be manually adjusted within a certain range. Change the resistance value by moving the position of the sliding contact. Depending on the requirements of the application, variable resistors can be provided with different levels of accuracy. It can be used in laboratory instruments, audio equipment, control systems, etc. The resistance value of thermistor will change with the change of temperature. For example, the negative temperature coefficient (NTC) will decrease with the increase of temperature. The positive temperature coefficient (PTC) will increase the resistance value as the temperature increases. Thermistors respond quickly to changes in temperature. After long-term use, thermistors may experience resistance drift. These special resistors play an important role in electronic devices and industrial applications.